2.3. 使用 OpenSSL 为 TLS 服务器证书创建私钥和 CSR

流程

1. 在服务器系统上生成私钥，例如：

   $ openssl genpkey -algorithm ec -pkeyopt ec_paramgen_curve:P-256 -out <server_private.key>

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2. 可选：使用您选择的文本编辑器，来准备一个简化创建 CSR 的配置文件，例如：

   $ vim <example_server.cnf>
   [server-cert]
   keyUsage = critical, digitalSignature, keyEncipherment, keyAgreement
   extendedKeyUsage = serverAuth
   subjectAltName = @alt_name
   
   [req]
   distinguished_name = dn
   prompt = no
   
   [dn]
   C = <US>
   O = <Example Organization>
   CN = <server.example.com>
   
   [alt_name]
   DNS.1 = <example.com>
   DNS.2 = <server.example.com>
   IP.1 = <192.168.0.1>
   IP.2 = <::1>
   IP.3 = <127.0.0.1>

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   extendedKeyUsage = serverAuth 选项限制证书的使用。

3. 使用之前创建的私钥创建 CSR：

   $ openssl req -key <server_private.key> -config <example_server.cnf> -new -out <server_cert.csr>

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   如果省略了 -config 选项，req 工具会提示您额外的信息，例如：

   You are about to be asked to enter information that will be incorporated
   into your certificate request.
   What you are about to enter is what is called a Distinguished Name or a DN.
   There are quite a few fields but you can leave some blank
   For some fields there will be a default value,
   If you enter '.', the field will be left blank.
   -----
   Country Name (2 letter code) [XX]: <US>
   State or Province Name (full name) []: <Washington>
   Locality Name (eg, city) [Default City]: <Seattle>
   Organization Name (eg, company) [Default Company Ltd]: <Example Organization>
   Organizational Unit Name (eg, section) []:
   Common Name (eg, your name or your server's hostname) []: <server.example.com>
   Email Address []: <server@example.com>

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验证

1. 从 CA 获取请求的证书后，检查证书的人类可读部分是否与您的要求匹配，例如：

   $ openssl x509 -text -noout -in <server_cert.crt>
   Certificate:
   …
           Issuer: CN = Example CA
           Validity
               Not Before: Feb  2 20:27:29 2023 GMT
               Not After : Feb  2 20:27:29 2024 GMT
           Subject: C = US, O = Example Organization, CN = server.example.com
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
   …
           X509v3 extensions:
               X509v3 Key Usage: critical
                   Digital Signature, Key Encipherment, Key Agreement
               X509v3 Extended Key Usage:
                   TLS Web Server Authentication
               X509v3 Subject Alternative Name:
                   DNS:example.com, DNS:server.example.com, IP Address:192.168.0.1, IP
   …

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